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The answer to yoour summing question is no you do not have to have a summing box. Generally a summing box is used to ballance the number of load cells you have. For example if you were using a Ricelake box it has multiple potentiometers inside the box and you use these to isolate each sensor and make resistence readings on the load cell in question. When done correctly all of the load cells will match in resistance at the same load point. Read the instructions on your summing box (if you use one) on how to do this.

However since you are doing concrete mixing the accuracy that you will have without bothering with the ballancing will be fine. You have so many other things that will throw you out when you are running a concrete or gypsum batching system. I do not have time to go through all of the finer points but the most important will be to either stop or dramatically slow the mixing blades as you reach the end of your fill for each of the individual ingredients (leave the mixer off entirely for the water fill process since water is the most important to be exact in a batch mix and you wont have any trouble starting the mixing blades after it is finished). Your cement powder and sand can be off by several pounds and not bother your overall mix too badly, but with mixing blades at full experience shows that the mixer needs to stop or slow at least 5 pounds before your final weight is achieved.

Good luck and have fun

Keith

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The answer to yoour summing question is no you do not have to have a summing box. Generally a summing box is used to ballance the number of load cells you have. For example if you were using a Ricelake box it has multiple potentiometers inside the box and you use these to isolate each sensor and make resistence readings on the load cell in question. When done correctly all of the load cells will match in resistance at the same load point. Read the instructions on your summing box (if you use one) on how to do this.

However since you are doing concrete mixing the accuracy that you will have without bothering with the ballancing will be fine. You have so many other things that will throw you out when you are running a concrete or gypsum batching system. I do not have time to go through all of the finer points but the most important will be to either stop or dramatically slow the mixing blades as you reach the end of your fill for each of the individual ingredients (leave the mixer off entirely for the water fill process since water is the most important to be exact in a batch mix and you wont have any trouble starting the mixing blades after it is finished). Your cement powder and sand can be off by several pounds and not bother your overall mix too badly, but with mixing blades at full experience shows that the mixer needs to stop or slow at least 5 pounds before your final weight is achieved.

Good luck and have fun

Keith

Thank you very much for your answer,

I'm thinking of using the summing box, due to it's low price, and it's advantages.

Wich summing box do you recommend for my application?,

I will use 3 load cells for weighing all ingredients, then to connect them to the summing box, and finally the box to the IO-LC1 module.

Thanks.

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I would say use a box from whatever manufacturer you are using to supply you actual load cells. If they do not make one then I woould use the Ricelake. The website is www.ricelake.com and just go to theor junction boxes and pick the product you think will work the best for you.

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Load cells are kind of magical when it comes to scaling (not really, but it is fun to say). The whole point to running the calibration is that it will calibrate to the exact weights you tell the system it is. So if you tell the system that calibration 1 is zero KG (this is not really zero this is the weight of the whole mixer assmbly with all of its parts and motors attached setting their weight on the load cell(s)) then the load cell(s) will recognize whatever the unloaded weight is of the mixer assembly as Zero Kg. Then for your second calibration point lets say you define that as 50Kg. Put a 50Kg weight onto the mixer (so you are now empty mixer assembly weight + 50Kg) and calibrate to the second point. Personally I calibrate 3 points but 2 will work (remember the first of your calibration points is always going to be zero Kg for the system to work and I like to have two more points).

By telling the PLC that you are calibrating to an integer value of 0 and an integer value of 50 and you just put text on your screen than the units are Kg and let the PLC do all the rest of the work. At this point you will be able to stand on the mixer and you should be able to accurately read your body weight in Kg.

A couple of notes:

1) your calibration weight(s) need to be placed as close to the center of the mixer as possible so that you do not load too heavily to one load cell or another (I am assuming you have more than one load cell on the mixer).

2) your integers must have the same number of places as what you want to show on screen. For example if you want to show xxxx.x Kg on your screen then your first calibration point will be 0 but your second calibration point will be 500 (50.0Kg).

Thanks

Keith

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Load cells are kind of magical when it comes to scaling (not really, but it is fun to say). The whole point to running the calibration is that it will calibrate to the exact weights you tell the system it is. So if you tell the system that calibration 1 is zero KG (this is not really zero this is the weight of the whole mixer assmbly with all of its parts and motors attached setting their weight on the load cell(s)) then the load cell(s) will recognize whatever the unloaded weight is of the mixer assembly as Zero Kg. Then for your second calibration point lets say you define that as 50Kg. Put a 50Kg weight onto the mixer (so you are now empty mixer assembly weight + 50Kg) and calibrate to the second point. Personally I calibrate 3 points but 2 will work (remember the first of your calibration points is always going to be zero Kg for the system to work and I like to have two more points).

By telling the PLC that you are calibrating to an integer value of 0 and an integer value of 50 and you just put text on your screen than the units are Kg and let the PLC do all the rest of the work. At this point you will be able to stand on the mixer and you should be able to accurately read your body weight in Kg.

A couple of notes:

1) your calibration weight(s) need to be placed as close to the center of the mixer as possible so that you do not load too heavily to one load cell or another (I am assuming you have more than one load cell on the mixer).

2) your integers must have the same number of places as what you want to show on screen. For example if you want to show xxxx.x Kg on your screen then your first calibration point will be 0 but your second calibration point will be 500 (50.0Kg).

Thanks

Keith

Hi Keith,

Thank you for answer my questions, I have other doubt.

I'm trying to make the program for my mixer, so the ingredients will be added to the mixer according to total weight in this mixer.

So, for example, the mixer will start putting sand in the mixer (X Kg sand), after this, no more sand is added and water starts to be dosed (Y Kg water), then the gravel is added (Z Kg), and finally the cement (W Kg).

Then,

How can I set this batch control?

Do I have to use the "Net Weight ML" to compare the actual weight with the goal weight of each ingredient?

What do you recommend in this case? Wich part of the help file of VisiLogic should I check?

Thank you so much your help is very usefull in this moment, because it´s the harder part of my project.

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This is more of a programming style question. Your batch can be broken down into a definite sequence, and I find the easiest way to program a sequence is to make it into a "state machine".

You start by drawing your sequence as a flowchart on paper and assigning step numbers to each operation. Then use a pointer in the PLC with equal blocks to only allow one step (state) to be active at a time.

You will define a state that adds each ingredient and jump from one state to the next to add additional ingredients.

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This is more of a programming style question. Your batch can be broken down into a definite sequence, and I find the easiest way to program a sequence is to make it into a "state machine".

You start by drawing your sequence as a flowchart on paper and assigning step numbers to each operation. Then use a pointer in the PLC with equal blocks to only allow one step (state) to be active at a time.

You will define a state that adds each ingredient and jump from one state to the next to add additional ingredients.

I have attached an example.

Joe T.

Thank you so much Joe!

What a usefull example!

I still don't understand:

In the harware configuration of my project I set ML 0 as the "LC 1st Input value (HWC)" or the Net Weight ML . In the example you set ML0 as The Scale Reading. Ok.

But,

Which are the units of ML 0? Will this ML be in Kg after calibration? I need to know this to know the values of the amounts MLs.

I appreciate your answers, and forgive me if I don´t undertstand some logic things .

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I think the thought that is giving you trouble is that the load cell is giving you an actual weight value. It is not. The load cell is giving the load cell modual's resistance data off of the load cell bridge deflecting when weight is placed on the cell. These values allways stay the same at the same weight, but you do not manipulate these values, they just are what they are.

So if what I said is true how do you get weight?? A load cell is not like a pressure transducer or temperature sensor. a pressure sensor has a difinative range. lets say that the sensor os a 0 to 10 BAR sensor you would have to define in your programming for a 0-10VDC output that 0 volts =0 Bar and 10V = 10 BAR. Load cell ranging does not work this way. Youir load cell has a maximum weight it has been rated for before the loac cell is damaged or breaks. You need this information to be sure that the weight of the mixer filled with the max aggregate product plus shock load does not exceed the maximum capability of the load cell(s) you are using. Beyond this that is all you care about.

So back to scaling. You scale the load cell or group of load cells automatically when you run the calibration that was talked about in the earlier post. The whole point of the calibration is for you to calibrate the load cell(s) you have to the input module (IO-LC1 in this case) you have. Overt time the load cell values may change so recalibration may be necessary periodically.

In this case you want cailbration point zero to be 0KG (even though you already have 200KG of mixer parts on top of the laod cell) so with everything that will normally be on the load cell when the mixer is empty is your first calibration point and you will tell the system that this is 0KG. Then you run your second calibration point with lets say a 10.0 KG weight you tell the system that the wieght you are applying is 10.0 KG (in you rladder you wil be telling that you are putting on a weight os 100 (10 + an extra zero to account for the decimal place). If you run a third calibratiion point at les say 50.0KG then you will tell the system that what you are putting on is 500 (50 + the extra zero for the decimal place).

By telling the system that these values are what to expect the system will record and save that at this resistance I should poulate ML0 with a value off 100 (when 10KG is on/in the mixer) aty the same time it will use the change in resistance (because you cailbrated it for these values) that a different resistance equals a value of 500 in ML0 when 50KG is in/on the mixer. The system is smart enough to auto fill in any other values because of your calibration efforts. So for example if you were to put your self in the mixer and you weigh 88.5KG (195 LB) then the sytem will populate a value into ML0 with 885.

In my world I would want pounds and not KG so for your exact test weights I would have cailbrated to:

Calibration first point 0

Calibration second point 220 (10KB = 22.0 US pounds)

Calibration third point 1102 (50KG = 110.2 pounds)

At this point by my having told the system that the calibration points were my values and not yours I will have automatically changed the on screen readings from KG to LB.

I hope this helps Im not sure how else to put it so it make sense. I would recomend just trying it and seeing for yourself it will make more sense faster than 50 conversations about it.n Playing with the calibration values is a great teacher as well.

Good luck

Keith

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I think the thought that is giving you trouble is that the load cell is giving you an actual weight value. It is not. The load cell is giving the load cell modual's resistance data off of the load cell bridge deflecting when weight is placed on the cell. These values allways stay the same at the same weight, but you do not manipulate these values, they just are what they are.

So if what I said is true how do you get weight?? A load cell is not like a pressure transducer or temperature sensor. a pressure sensor has a difinative range. lets say that the sensor os a 0 to 10 BAR sensor you would have to define in your programming for a 0-10VDC output that 0 volts =0 Bar and 10V = 10 BAR. Load cell ranging does not work this way. Youir load cell has a maximum weight it has been rated for before the loac cell is damaged or breaks. You need this information to be sure that the weight of the mixer filled with the max aggregate product plus shock load does not exceed the maximum capability of the load cell(s) you are using. Beyond this that is all you care about.

So back to scaling. You scale the load cell or group of load cells automatically when you run the calibration that was talked about in the earlier post. The whole point of the calibration is for you to calibrate the load cell(s) you have to the input module (IO-LC1 in this case) you have. Overt time the load cell values may change so recalibration may be necessary periodically.

In this case you want cailbration point zero to be 0KG (even though you already have 200KG of mixer parts on top of the laod cell) so with everything that will normally be on the load cell when the mixer is empty is your first calibration point and you will tell the system that this is 0KG. Then you run your second calibration point with lets say a 10.0 KG weight you tell the system that the wieght you are applying is 10.0 KG (in you rladder you wil be telling that you are putting on a weight os 100 (10 + an extra zero to account for the decimal place). If you run a third calibratiion point at les say 50.0KG then you will tell the system that what you are putting on is 500 (50 + the extra zero for the decimal place).

By telling the system that these values are what to expect the system will record and save that at this resistance I should poulate ML0 with a value off 100 (when 10KG is on/in the mixer) aty the same time it will use the change in resistance (because you cailbrated it for these values) that a different resistance equals a value of 500 in ML0 when 50KG is in/on the mixer. The system is smart enough to auto fill in any other values because of your calibration efforts. So for example if you were to put your self in the mixer and you weigh 88.5KG (195 LB) then the sytem will populate a value into ML0 with 885.

In my world I would want pounds and not KG so for your exact test weights I would have cailbrated to:

Calibration first point 0

Calibration second point 220 (10KB = 22.0 US pounds)

Calibration third point 1102 (50KG = 110.2 pounds)

At this point by my having told the system that the calibration points were my values and not yours I will have automatically changed the on screen readings from KG to LB.

I hope this helps Im not sure how else to put it so it make sense. I would recomend just trying it and seeing for yourself it will make more sense faster than 50 conversations about it.n Playing with the calibration values is a great teacher as well.

Good luck

Keith

Thanks a lot Keith,

Now I understand so much better this topic, I'm gonna start to work with my load cells directly, and I'll tell you how my project goes.

After the complete calculation for C is made divide the result by 10 to end up with the C value you want with one decimal place.

EXAMPLE:

20 pound original weight

35% moisture content

(20*(100+35))/10 = 270 = 27.0 on screen value

Since you may have entry values to one decimal place it is divide by 10 (if you had on screen entry values to two decimal places don't divide at all to get the C value you want. If you have zero decimal places for your enterable values than divide by 100 to remove the last decimal place just keep in mind you will always be off by whatever the remainder would have been if you have no decimal places).

After the complete calculation for C is made divide the result by 10 to end up with the C value you want with one decimal place.

EXAMPLE:

20 pound original weight

35% moisture content

(20*(100+35))/10 = 270 = 27.0 on screen value

Since you may have entry values to one decimal place it is divide by 10 (if you had on screen entry values to two decimal places don't divide at all to get the C value you want. If you have zero decimal places for your enterable values than divide by 100 to remove the last decimal place just keep in mind you will always be off by whatever the remainder would have been if you have no decimal places).

Keith

Thank u once again Keith, I´ll start to work on this with your valious answer.

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I'm working also now on a similar project like this. The customer both V130 PLC Unitronics. For the weight system on the hoppers, I'm using S type sensors.

Although I have not so much complex plant. It is only 4 hoppers with sand, one hopper with cement and adding water. However, I have problems, because the customer that I have, has no functional description of the plant and he doesn't know how it is suppose to work. Me also:)

1. So, my first question to you is does anyone has a functional description for a concrete batching plant?

2. The S sensors has Weighing Indicator that has RS232 and RS485 interface. This I have to use for communicating with the PLC. Is there any example how it has to be done for V130?

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I)Research design

The system will haveinterfacing unit, power control unit,which includes keyed power switch with internal circuit breaker, auxiliary control unit, which includes all controls includes status lights, which includes cement gate closed/opened, aggregate gate opened/closed, and load complete, weight control unit (weight measuring device) for each component of the concrete ,Cement and Aggregate control contains status light in each gate and weigh discharge gate control andmixer control unit, which includes fully integrated mixer control, mixer start/stop control and mixer discharge control.

Here, in our project we have reservoir for each components of concrete. Using interfacing system (using micro controller), and weight measuring device, the weight of each component is measured with certain delay the discharging of each components of the concrete by weight with required set point in to common hopper is stored. If the ratio of each component is reached to the desired ones, the motor starts and the shaft blade rotates and mixing is done. Unless the ratio is correct, mixing is not done. When the set time of the mixing is reached, the concrete discharge gate is opened. so what mechanism you recommend to use control the gate of each ingredient and what types of gate you recommend for me,,,,,, what will happen if i will use electrical actuated butterfly valve? and what type of load cell is used for weight measurement of each ingredients? please help me am new for all thing